Invocations

Invocations denotes how skillful your character is at beseeching a deity for help. It improves the power and/or success rate of most god-given powers, save for Trog's, Kiku's, and Nemelex's, which are based entirely on Piety, Necromancy, and Evocations, respectively.

Invocations also increases your max MP, but the effect is not cumulative with Spellcasting.

Invocations aptitudes

From Dungeon Crawl Stone Soup in-game documentation:

Hu	Ce	Dg	Ds	Dr	DD	DE	HE	SE	Fe	Gh	Ha	Ko	Mf	Mi	Mu	Na	Op	Og	HO	Sp	Te	Tr	Vp
1	1	N/A	3	1	3	1	1	1	0	1	1	1	1	0	-1	1	1	1	3	0	-1	-1	-1